<template>
  <div class="slider" ref="slider">
    <div class="slider-group" ref="sliderGroup">
      <slot>
      </slot>
    </div>
    <div class="dots">
      <span class="dot" :class="{active: currentPageIndex === index}"  v-for="(item, index) in dots">{{currentPageIndex}}</span>
    </div>
  </div>
</template>

<script type="text/ecmascript-6">
  import {addClass} from "common/js/dom";
  import BScroll from "better-scroll";

  export default {
    name: "slider",
    props: {
      loop: {
        type: Boolean,
        default: true
      },
      autoPlay: {
        type: Boolean,
        default: true
      },
      interval: {
        type: Number,
        default: 4000
      },
      showDot: {
        type: Boolean,
        default: true
      },
      click: {
        type: Boolean,
        default: true
      }
    },
    data() {
      return {
        dots: [],
        currentPageIndex: 0
      };
    },
    mounted() {
      setTimeout(() => {
        this._setSliderWidth();
        this._initDots();
        this._initSlider();

        if (this.autoPlay) {
          this._play();
        }
      }, 20);

      window.addEventListener("resize", () => {
        if (!this.slider) {
          return;
        }
        this._setSliderWidth(true);
        this.slider.refresh();
      });
    },
    destroyed() {
      clearTimeout(this.timer);
    },
    methods: {
      _setSliderWidth(isResize) {
        this.children = this.$refs.sliderGroup.children;

        let width = 0;
        let sliderWidth = this.$refs.slider.clientWidth;
        for (let i = 0; i < this.children.length; i++) {
          let child = this.children[i];
          addClass(child, "slider-item");

          child.style.width = sliderWidth + "px";
          width += sliderWidth;
        }
        if (this.loop && !isResize) {
          width += 2 * sliderWidth;
        }
        this.$refs.sliderGroup.style.width = width + "px";
      },
      _initSlider() {
        this.slider = new BScroll(this.$refs.slider, {
          scrollX: true,
          scrollY: false,
          momentum: false,
          snap: {
            loop: this.loop,
            threshold: 0.3,
            speed: 400
          },
          bounce: false,
          click: this.click
        });

        this.slider.on("scrollEnd", () => {
          let pageIndex = this.slider.getCurrentPage().pageX;
          this.currentPageIndex = pageIndex;
          if (this.autoPlay) {
            this._play();
          }
        });
        this.slider.on("touchend", () => {
          if (this.autoPlay) {
            this._play();
          }
        });
        this.slider.on("beforeScrollStart", () => {
          if (this.autoPlay) {
            clearTimeout(this.timer);
          }
        });
      },
      _initDots() {
        this.dots = new Array(this.children.length);
      },
      _play() {
        clearTimeout(this.timer);
        this.timer = setTimeout(() => {
          this.slider.next();
        }, this.interval);
      }
    }
  };
</script>

<style scoped lang="scss" rel="stylesheet/scss">
  .slider{
    position: relative;
    min-height: 1px;
    .slider-group{
      position: relative;
      overflow: hidden;
      white-space: nowrap;
      .slider-item{
        float: left;
        box-sizing: border-box;
        overflow: hidden;
        text-align: center;
        a{
          display: block;
          width: 100%;
          overflow: hidden;
          text-decoration: none;
        }
        img{
          display: block;
          width: 100%;
        }
      }
    }
    .dots{
      position: absolute;
      right: 0;
      left: 0;
      bottom: 12px;
      text-align: center;
      font-size: 0;
      .dot{
        display: inline-block;
        margin: 0 4px;
        width: 8px;
        height: 8px;
        border-radius: 50%;
        background: #fff;
        &.active{
          width: 20px;
          border-radius: 5px;
          background:  #fff;
        }
      }
    }
  }
</style>
